If you follow the current timeline, it should go-
Hurt->Eccleston->Tennant->Tennant->Smith->Capaldi->Whitaker->Tennant->Tennant/Gatwa
Hurt was the real 9th doctor, but we call Eccleston the 9th doctor. And (if I get this all right) Tennant regenerated as himself twice, so he should be the 11th, 12th, 15th and Doctor 16 and a half. But people call him the 10th doctor. And Jodie Whitaker should have been the 14th Doctor, but people call her the 13th Doctor. And then Tennant came back and then there was the bigeneration of him and Gatwa.
And just to add to it all, there’s also a female clone of Tennant out there somewhere.
Is anyone else as confused as I am?
EDIT: Oh god, I just realized it gets even more confusing because now there’s all the Doctors before Hartnell.
Gatawa is the 15th Doctor. (Even though there are more versions of himself).
In Matt Smith’s final episode “The Time of the Doctor”, he did acknowledge he was the 13th version of himself, but only the 11th “Doctor”. Therefore no more regenerations. (Until the Timelords sent him more)
I have not seen Jodie’s run, and can not comment on the storyline from her Doctor.
I did find this article listing all versions of the Doctor. https://www.dexerto.com/tv-movies/doctor-who-every-doctor-and-actor-who-has-played-them-2030888/.
Hope this helps.
Spoiler about Whitaker in case you don’t want to know:
spoiler
Based on Whitaker’s run, there are more Doctors before Hartnell. His memory of them was just erased. So that doesn’t work either. Also, the ‘no more regenerations’ thing doesn’t work even though it was in that episode because we find out that the Doctor is not Gallifreyan, but comes from another universe and has an unlimited number of regenerations. And it looks like Davies has accepted that.
Which is what makes this far more confusing.
Looking at the full picture, “The Doctor” is on 15. The version number of the Timelord that goes by the Doctor is not currently known.
The link I posted references all of them.